Prepare the beef: Let the tenderloin sit at room temperature for 1 hour before cooking. Preheat the oven to 450°F (230°C).
Season the beef: Pat the beef tenderloin dry with paper towels. Rub it with olive oil, then generously season with salt and fresh ground black pepper.
Add aromatics: In a small bowl, mix minced garlic and chopped rosemary. Rub this mixture all over the tenderloin.
Tie the tenderloin: Place the tenderloin over pieces of precut kitchen twine spaced one inch apart and tie them closed. Alternatively, ask your butcher to tie the tenderloin for you.
Sear the beef: Heat vegetable oil in a 12-inch cast iron skillet over medium-high heat. Once the oil is hot, add the beef tenderloin and sear for 3 to 4 minutes per side, until browned all over.
Roast: Transfer the skillet to the preheated oven and roast for 25 to 30 minutes, or until the internal temperature reaches 130°F (54°C) for medium-rare. Use a meat thermometer to check for desired doneness.
Rest the meat: Remove the skillet from the oven and transfer the tenderloin to a cutting board. Tent a piece of foil over the meat and let it rest for 10 to 15 minutes.
Serve: Slice the tenderloin into ½-inch pieces and serve warm. Enjoy!